Fire protection sprinklers are often needed to be located in cold environments where the temperature is subject to falling below the freezing point of water (32° F., 0° C. at sea level), referred to herein as a freezing temperature. Such cold environments include open areas, freezers, cold rooms, passageways, or other areas exposed to freezing temperatures, such as unheated buildings in freezing climates or cold-storage rooms. If a conventional sprinkler system is located in such a cold environment, the water will freeze in the sprinkler head and/or pipe and render the sprinkler unable to actuate or damage the sprinkler and/or piping.
Conventional sprinkler systems are fully filled (charged) with liquids (for example, water) and are referred to as “wet sprinkler systems.” As is known in the art, these systems include sprinkler heads and piping.
One approach for dealing with cold environments is referred to as a “dry sprinkler system.” Dry sprinkler systems are designed such that in the unactuated state, the water is kept out of the portion of the system that is located in the cold environment. Only upon activation does the water enter the portion of the system that is located in the cold environment. Dry sprinklers and sprinkler systems are disclosed in, for example, U.S. Pat. No. 7,559,376, and also include sprinkler heads and piping.
Wet sprinklers, on the other hand, are designed to be filled with a liquid when in the unactuated state. For wet sprinklers that are not placed in cold environments, the sprinkler can be filled with water.
Another approach for cold environments is the deployment in wet sprinkler systems of liquids having freezing points below the freezing point of water, and often are referred to as “antifreezes” or “liquid freeze protectants.” Early industrial antifreezes included the use of alcohols, such as methanol. Methanol, however, is flammable, toxic, and tends to be corrosive. Ethylene glycol and propylene glycol have supplanted methanol as an antifreeze.
The National Fire Protection Association (NFPA) has permitted antifreeze in sprinkler systems since at least as early as 1952. Arvidson, J. Fire Protect. Eng. 21(2):115-32 (2011). The NFPA currently permits a maximum of 38% by volume propylene glycol and a maximum of 48% by volume glycerin (glycerol) for fire sprinklers, and 48% vol. glycerin and water antifreezes are currently on the market. However, these two water additives, at their highest allowable concentrations have freezing points of 0° F. (propylene glycol) and −15° F. (glycerin). The field, however, has experienced various difficulties with these chemical components. First, propylene glycol cannot be used in systems having chlorinated polyvinyl chloride (CPVC) pipes. Moreover, these two components, at their highest allowable concentrations, have the potential of adding heat to a fire, which is measured as the “heat release rate.”
As reported by Arvidson, antifreezes have resulted in flashovers upon sprinkler activation. In a tragic incident in Truckee, Calif., an explosion occurred with a residential sprinkler system containing an antifreeze, which resulted in a fatality and another victim badly burned.
U.S. Patent Application Publication 2014/0138105 A1 discloses the use of carboxylate salts in propylene glycol and glycerol-containing fluids. This publication discloses glycerol concentrations up to 60% wt., the use of 5% wt. to 50% wt. of a carboxylate salt, like potassium formate, and a reserve of alkalinity to ensure that pH does not drop below 8.
It is therefore desirable to develop antifreezes that have lower concentrations of glycerin and salts, and yet have a lower freezing point while avoiding flashovers and adding less heat to fires. It is also desirable to avoid the use of ethylene and propylene glycol.
Glycerol (glycerin) has a molecular formula of C3H8O3 and an IUPAC name of propane-1,2,3-triol. The structure is depicted below:
